This invention relates to fire event sensing devices and, more particularly, to a system for automatically monitoring the operability of fire event sensors housed within a fire event detection unit.
Although the percentage of U.S. households having at least one fire detection device of some type has grown to over 92%, the percentage of deaths caused by residential fires has remained steady. The fact that approximately one-third of all fire detection devices are non-operational when needed is a key reason for this unfortunate statistic. A large number of fire-related incidents involving property damage, personal injury, or even death are attributable to malfunctioning fire detection units. Malfunctioning smoke, heat, carbon monoxide, or other fire event sensors, or even dead or disconnected batteries, are often the result of a lack of manual testing by residents. It is therefore desirable to have a system for automatically testing the operability of sensors housed within a fire detection unit whether they are smoke, heat, carbon monoxide or other fire event sensors.
Several methods and devices have been proposed to monitor the operability of various fire event sensing devices. In U.S. Pat. No. 4,595,914 to Siegel, a self-test circuit for a fire event detector is disclosed for automatically periodically testing whether the sensitivity of an ionizationtype sensor is within a certain predetermined range. A fire event smoke alarm which automatically periodically tests the detector's operation or periodically sounds the detector's alarm to remind the occupant to manually test the alarm is disclosed in U.S. Pat. No. 4,965,556 to Brodecki. The prior art further includes several methods and devices for manually checking the functionality of combustion detection circuitry.
Although assumably effective in operation, such known methods and devices are incapable of monitoring the integrity and functionality of multiple types of fire event sensors housed within a single detection unit. In addition, the above referenced devices only provide a single test of integrity or operability, such as simulating a fire event within a predetermined fixed range of sensitivity or merely detecting whether any signal is received from a sensor. Significantly, the acceptable range of sensor sensitivity, actions to be taken based on self-test results, and the frequency of periodic checking can not be modified or adjusted without the replacement or addition of new circuitry. Further, the referenced devices do not allow the residential occupant to verify that the self-checking circuitry itself is functioning properly.
It is therefore desirable to have a system which automatically checks multiple parameters related to the integrity and operability of fire event sensors housed within a fire detection unit. It is also desirable that the monitored parameters be modifiable without the replacement or addition of any circuitry.